Automated assay techniques are crucial for disease analysis, bio-research and drug development in the medical and pharmaceutical industries. With incorporation of high-throughput steps, automated assay techniques can provide more results in a given amount of time than manual assay techniques. Automated assay techniques can reduce the risks of exposing personnel to potentially hazardous biological materials or chemicals. Modern automated assay devices can transport materials, such as biological samples, assay reagents, buffers, wash solutions, and the like, between a number of stations located in the devices. For instance, in a typical simple automated device a probe may aspirate sample from a sample vial located at a first station in the device, travel to and dispense the sample in a reaction container located at a second station in the device, travel to a wash station at a third location to aspirate and dispense a wash solution, and then return to the first station to aspirate sample from another sample vial. Three, four or more aspiration and dispensing stations can be found in commercially available automated devices. An exemplary automated device in described in U.S. Pat. Pub. No. 20050123445, published Jun. 9, 2005.
Typically, the probe should be thoroughly washed between aspirations and dispensations of different samples to avoid carryover or contamination. This is in part because carryover can adversely affect (usually add to) the volume of the dispensed sample. For instance, inaccurate results can occur where the volume of carryover sample is significant when added to the volume of dispensed sample. In addition, assay errors can occur due to cross-contamination between different samples being tested. While washing a probe is essential to obtaining accurate results in an automated assay device, it is also advantageous to reduce the time it takes to handle consecutive samples. Thus, it is desirable to reduce the time it takes to automatically wash the probe such as by reducing the distance the probe travels during the wash cycle.